The present invention relates to thin film magnetic transducers for reading and writing digital data on a magnetic disc. Specifically, a thin film magnetic transducer is described having a center tapped winding of an increased number of turns which does not limit transducer efficiency.
Data processing systems which call for additional memory capacity have correspondingly increased the data density for the system memory. In the magnetic disk art, the need for increased data density is reducing the track width for recording and reading data, thereby reducing the magnitude of signals from the transducer. An additional requirement of thinner magnetic disc media for high density memory applications will tend to reduce still further the magnitude of these signals. It is also advantageous to have the transducer write efficiently with relatively low write currents.
A solution for generating additional signal amplitude and writing with low current is to add additional turns to the winding disposed between pole pieces of a thin film transducer. The addition of more windings, however, has limitations. The transducer efficiency is controlled, in part, by the length of the region between the pole piece back gap region and pole tip region. As the distance between these two regions increases to make room for additional winding turns, a decrease in efficiency is realized.
One solution to the need for reading and writing efficiently with thin film transducers is described in the article entitled "Fabrication of Eight Turn Multi-Track Thin Film Heads", IEEE Transactions on Magnetics, Volume Mag. - 15 Number 6, November 1979, pages 1616 through 1618. The article describes a magnetic head which employs a plurality of windings, each stacked in parallel layers separated by a corresponding number of insulation layers. Such multiple insulation layers and conductor layers provide for steep transition regions connecting the back gap and pole tip portions of the magnetic transducers. This geometry imposes additional difficulty on conventional disposition techniques which are preferably carried out with more gently sloping transitions between the pole tip and back gap regions of the transducer element. With the structure described in this reference, the existence of numerous insulation layers poses a considerable risk of shorting between adjacent windings or between the windings and an adjacent pole piece.
In providing a magnetic transducer having additional turns, it is advantageous that a center tapped structure be provided which will permit half the turns to be used during a writing sequence, and to use all the turns in a sensing mode during a data read operation. Ideally, writing should be possible using either half of the winding in a center tapped structure, without a different drive circuit for each winding half. In order to achieve this flexibility, each winding half of a center tapped structure should have the equivalent impedance, in both inductive and resistive components.
The requirement for equal resistance between winding portions has been recognized in U.S. Pat. No. 4,318,148. The present invention seeks to provide for both an equal resistance and equal inductance for each half of a center tapped thin film magnetic transducer winding.